1. Field of the Invention
The present invention is generally related to an extended sterndrive transom assembly with trim and steering cylinders and, more particularly, to a system which advantageously positions trim and steering cylinder components and related hydraulic devices for more effective control of the outdrive unit.
2. Description of the Prior Art
Various types of sterndrive marine propulsion systems are well known to those skilled in the art. In addition to the sterndrive systems available in commercial quantities from manufacturers, such as the Mercury Marine division of Brunswick Corporation, several aftermarket products are available which can be installed for use in conjunction with sterndrive systems.
U.S. Pat. No. 3,888,203, which issued to Lohse on Jun. 10, 1975, discloses a sterndrive for boats. Two hydraulic cylinders, one on each side of the sterndrive and disposed between the tilt housing and the dirigible unit, steer the latter on the axis of the vertical drive shaft. The tilt housing is carried by lateral trunnions rotatable in bearings of the transom mounting on a transverse axis generally passing near the center of the universal joint in the horizontal driveshaft which extends through the transom. A trim adjustment and power tilt cylinder is disposed between the tilt housing and the transom mounting. The dirigible unit is suspended by the vertical driveshaft from an upper gear housing which, in turn, is removably secured to the tilt housing. The vertical driveshaft is protected from thrust and impact stresses by a steering support tube constituting a part of the dirigible unit and surrounding the shaft within a sleeve of the upper gear housing.
U.S. Pat. No. 4,645,463, which issued to Arneson on Feb. 24, 1987, describes a marine outdrive apparatus. The outdrive is attachable to the transom of a boat having an inboard engine. The marine outdrive includes a tubular support casing securable to and extendable rearwardly of the boat""s transom and having a ball socket at its rear end. The ball socket receives a ball at the front end of a tubular, propeller shaft carrier having a conical outer surface. A driveshaft connectable to the inboard engine is journalled in the support casing. A propeller shaft is journalled in the propeller shaft carrier and has a propeller mounted thereon at the rear end of the propeller shaft carrier. A universal joint couples the two shafts together, the center of such joint substantially coinciding with the point about which the ball pivots within the socket. Hydraulic steering cylinders are attached to the propeller shaft carrier to pivot the latter about a steering axis extending through the pivot point of the ball. A hydraulic trim cylinder extends between the transom and the propeller shaft carrier to swing the propeller shaft carrier about a laterally extending trim axis extending through the pivot point of the ball. The upper end of the trim cylinder is pivotally mounting on the transom at a location above and vertically aligned with the pivot point of the ball or at a location above and forwardly of such pivot point. Improved fins are provided on the propeller shaft carrier near the propeller to stabilize the boat. The driveshaft of the inboard motor can be directly connected to the joint or offset from the joint and coupled thereto by a vertically extending transmission.
U.S. Pat. No. 5,755,604, which issued to Borgersen on May 26, 1998, describes a boat propeller drive unit. The drive unit comprises a frame-like carrier intended to be fixedly joined to a boat transom, and a propeller rig which is suspended in a fork for trim and tilting movement relative to the fork about a horizontal axis. The fork, in turn, is mounted in the carrier for pivoting about a vertical steering axis. A pair of hydraulically operated piston cylinder devices are pivotally joined at opposite ends to the rig and to the legs of the fork.
U.S. Pat. No. 5,372,529, which issued to Binversie et al on Dec. 13, 1994, describes a trim assembly. A marine propulsion device comprises a transom bracket adapted to be mounted on a boat transom, a swivel bracket supported on the transom bracket for pivotal movement about a generally horizontal tilt axis, a propulsion unit mounted on the swivel bracket for pivotal movement relative thereto about a generally vertical steering axis, a cylinder which is mounted on one of the swivel brackets and the transom bracket and which has a tapered inner surface defining an open end, a piston slidably housed by the cylinder, a rod having a first end connected to the piston and a second end extending from the open end of the cylinder, a mechanism for transmitting thrust forces from the other of the transom brackets the swivel bracket to the second end of the rod, and an end cap surrounding the rod and having a tapered outer surface engaged with the tapered inner surface of the cylinder.
U.S. Pat. No. 5,002,510, which issued to Rump on Mar. 26, 1991, describes a steering mechanism for a marine propulsion device. The invention provides a hydraulic steering assembly for a marine propulsion unit in which the axis of the cylinder travels parallel to the axis of the propulsion unit tilt axis during pivotal steering of the propulsion unit. The steering assembly provides two, two-bar link arms interconnecting the tilt tube and cylinder rod.
U.S. Pat. No. 4,615,290, which issued to Hall on Oct. 7, 1986, describes a marine propulsion steering assist device. The device comprises a propulsion unit pivotable about a first steering axis to steer a marine vehicle. It also comprises a trim tab mounted on the propulsion unit and pivotable about a second steering axis for assisting in steering the vehicle. The invention comprises a hydraulic sensing arrangement for sensing torque on the propulsion unit relative to the first steering axis to pivot the trim tab in response to the torque.
U.S. Pat. No. 4,498,871, which issued to Hall et al on Feb. 12, 1985, describes a hydraulic system for marine propulsion device with sequentially operating tilt and trim means. A marine propulsion device comprises a first pivot connecting a stem bracket to a transom bracket for pivotal movement therebetween about a first pivot axis which is horizontal when the transom bracket is boat mounted, a second pivot connecting the swivel bracket to the stem bracket for pivotal movement of the swivel bracket with the stem bracket and relative to the stern bracket about a second pivot axis parallel to the first pivot axis. A propulsion unit includes, at the lower end thereof, a rotatably mounted propeller and connected to the swivel bracket for steering movement therebetween and for common pivotal movement. A trim cylinder piston assembly is pivotally connected to the stem bracket and to the swivel bracket and includes first and second ends. A tilt cylinder piston assembly is pivotally connected to the transom bracket means and to the stem bracket and includes first and second ends. A hydraulic system is provided for sequentially operating the tilt and trim cylinder piston assemblies.
U.S. Pat. No. 3,847,107, which issued to Buddrus on Nov. 12, 1974, describes a hydraulic marine propulsion and guidance system. The system is intended for use with a marine vessel and consists of a fluid pressure generating system and a helm pressure generating unit located within the vessel, a tilting fluid actuator mounted to the transom of the vessel, a lift clevis operatively connected to the shaft of the tilting actuator, and a rotary fluid actuator mounted within the lift clevis. A steering clevis is operatively connected to the shaft of the rotary fluid actuator and a fluid motor propeller assembly is secured to the steering clevis. An additional fluid pump is located within the vessel and fluid conduits are operatively connecting the same to the tilting actuator such that as the pump is operated the shaft of the tilting actuator rotates the lift clevis in turn tilting the fluid motor propeller assembly. Further fluid conduits are operatively connecting the helm pressure generating unit and the rotary actuator such that as the helm pressure generating unit is operated the shaft of the rotary actuator rotates the steering clevis and the fluid motor propeller assemblies. The fluid conduit includes single passage oscillating swivels mounted to the transom along a common axis defining the center of rotation of the lift clevis. Still further conduits are used to connect the fluid pressure generating system and the fluid motor including a multiple passage oscillating swivel operatively mounted to the steering clevis and aligned with respect to the axis of rotation of the steering clevis.
U.S. Pat. No. 6,287,160, which issued to Onoue on Sep. 11, 2001, describes a tilt and trim arrangement for a marine propulsion system. The arrangement for a marine propulsion system includes an improved construction. A swivel bracket, which carries a drive unit for pivotal movement about a steering axis includes a pair of ribs spaced apart transversely from each other. A clamping bracket is affixed to an associated watercraft and supports the swivel bracket for pivot movement about a tilt axis. A hydraulic tilt device is provided for tilting the swivel bracket. The tilt device includes a cylinder housing, a piston slidably supported within the housing, and a piston rod affixed to the piston. The cylinder housing has an upper section with a diameter that is smaller than a lower section, and the piston rod extends outwardly from the upper section. The piston rod is pivotally affixed to the ribs. The upper section of the cylinder housing is generally positioned between the ribs at least when the piston rod is fully retracted within the cylinder housing.
U.S. Pat. No. 4,836,810, which issued to Entringer on Jun. 6, 1989, discloses a combined power trim and steering system. The power steering and trim functions of a marine drive unit are combined in a fluid pressure supply system which utilizes a single electric motor drive hydraulic pump to provide operating fluid for both functions. Fluid pressure to operate the power steering is supplied by an actuator which is, in turn, charged by the hydraulic pump. The pump is also operable in response to operator input to supply fluid pressure from the trim system. Appropriate controls responsive to the upper and lower pressures limits of the accumulator, are used both for charging the accumulator and for providing operational priority to the power steering system by disabling operation of the trim system during charging of the accumulator.
U.S. Pat. No. 5,358,435, which issued to Rodskier on Oct. 25, 1994, describes a boat propulsion unit. The unit comprises a suspension arrangement and a propeller drive shaft housing which, via a lower end and upper universal joint, are pivotally connected to each other. A hydraulic piston cylinder arrangement has its cylinder connected to the upper joint and, at the lower end of its piston rod, presents a forked bracket which is pivotally connected to an upper region of the driveshaft housing. At a distance from the upper joint, the cylinder of the arrangement presents attachments for a steering mechanism, by means of which the arrangement is displaceable about a vertical axis. The embodiment implies that the piston cylinder arrangement serves both as a trim and tilt cylinder are well as a rudder.
Various types of hydraulic steering systems are available to owners from companies that provide aftermarket goods. Certain types of hydraulic steering assemblies, intended for use with marine propulsion systems, are available in commercial quantities from the Inman Marine Corporation. The steering assemblies available from the Inman Marine Corporation can be added to existing marine propulsion systems in order to provide certain types of steering systems for marine vessel.
U.S. Pat. No. 5,466,178, which issued to Inman et al on Nov. 14, 1995, describes a load-relieving external steering system for marine outdrive units. A load-relieving external steering systems for marine outdrive units comprises a first hydraulic steering ram having a piston partially disposed within a housing, wherein the piston is attached to one side of an outdrive unit and the housing is attached to an adjacent portion of a transom. A second hydraulic steering ram has a piston partially disposed within a housing, wherein the piston of the second steering ram is attached to an opposite side of the outdrive unit and the housing of the second steering ram is attached to an adjacent portion of the transom. The first and second steering rams are mounted in a common horizontal plane between the outdrive unit and the transom. The housing of each steering ram comprises a front chamber and a rear chamber. A hydraulic pump for providing hydraulic fluid at a constant pressure is connected to the rear chamber of each steering ram. A hydraulic pump and a control valve for providing hydraulic fluid at a variable pressure is connected to the front chamber of each steering ram, wherein the hydraulic pressure at a variable pressure is routed to a particular front chamber to effect the steering of the vessel in a desired direction. At all times the hydraulic fluid at constant pressure routed to each rear chamber imposes a forwardly directed compression force onto an upper steering bearing to counteract a static and/or dynamic tension load and, thereby enhance the service lift of the upper steering bearing.
The patents described above are hereby expressly incorporated by reference in the description of the present invention.
A marine propulsion system, made in accordance with the preferred embodiment of the present invention comprises a drive unit that is attachable to a transom of a marine vessel. The drive unit comprises a fixed portion and a moveable portion. The moveable portion of the drive unit is independently rotatable about both a generally vertical steering axis and a generally horizontal trimming axis. Although the steering axis is described as being generally vertical and the trimming axis is described as being generally horizontal, it should be understood that variations from the absolute vertical and horizontal planes are also within the scope of the present invention.
A steering cylinder assembly extends between first and second structural members of the propulsion system. A first end of the steering cylinder assembly is pivotally attached to the first structural member which is rigidly attached to the transom of a marine vessel. A second end of the steering cylinder assembly is pivotally attached to the second structural member which is rigidly attached to a moveable portion of the drive unit. The moveable portion of the drive unit is rotatable about the steering axis in response to a change in the effective distance is between the first and second structural members.
A trim cylinder assembly extends between the second structural member and a third structural member. A first end of the trim cylinder assembly is pivotally attached to the second structural member and a second end of the trim cylinder assembly is pivotally attached to a third structural member which is rigidly attached to the moveable portion of the drive unit. The moveable portion of the drive unit is rotatable about the trimming axis in response to a change in the effective distance between the second and third structural members.
The moveable portion of the drive unit comprises a steering segment and a trimming segment. The steering segment is rotatable about the steering axis and the trimming segment is rotatable about the trimming axis. The second structural member is rigidly attached to the steering segment and the third structural member is rigidly attached to the trimming segment.
The steering cylinder assembly comprises a steering piston disposed within a steering cylinder, with the steering piston being moveable relative to the steering cylinder in order to cause the change in the effective distance between the first and structural members. As is well known to those skilled in the art, the steering piston is attached to a rod, or shaft, which moves in coordination with the steering piston in response to changes in pressure within the steering cylinder. The steering piston is pivotally attached to the second structural member and the steering cylinder is pivotally attached to the first structural member.
The trim cylinder assembly comprises a trim piston disposed within a trim cylinder, with the trim piston being moveable relative to the trim cylinder in order to cause the change in the effective distance between the second and third structural members. The trim piston is pivotally attached to the third structural member and the trim cylinder is pivotally attached to the second structural member. The second end of the steering cylinder assembly is pivotable about a first axis which is fixed in relation to the second structural member. The first end of the trim cylinder assembly is pivotable about a second axis which is in fixed relation with the second structural member. The first and second axes are in fixed relation with each other and with the second structural member.
Certain embodiments of the present invention further comprise a hydraulic pump and a hydraulic conduit which has a first portion and a second portion. The pump is typically attached to an engine and driven by an accessory belt which is driven by the engine. The hydraulic conduit is connected between the steering cylinder assembly and the hydraulic pump. A steering mechanism is operatively associated with the hydraulic conduit to affect a pressure magnitude within the hydraulic conduit and cause the steering cylinder assembly to change the effective distance between the first and second structural members. A pressure relief valve is connected in fluid communication with the hydraulic conduit for limiting a hydraulic pressure magnitude within the hydraulic conduit. The first portion of the hydraulic conduit is connected in fluid communication between the steering mechanism and the pressure relief valve. The second portion of the hydraulic conduit is connected in fluid communication between the steering cylinder assembly and the pressure relief valve. The first portion of the hydraulic conduit is greater in length than the second portion of the hydraulic conduit and, in a particularly preferred embodiment of the present invention, the first portion of the hydraulic conduit is at least twice as long as the second portion of the hydraulic conduit.
It should be understood that the steering cylinder assembly and the trim cylinder assembly of the present invention typically are arranged in association with a symmetrical duplicate of each cylinder assembly. In other words, two steering cylinder assemblies (port and starboard) and two trim cylinder assemblies (port and starboard) are used in most applications of the present invention.